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Experimental Study of Roughness Effect on Turbulent Shear Flow Downstream of a Backward Facing Step

An experimental study was undertaken to investigate the effect of roughness on the characteristics of separated and reattached turbulent shear flow downstream of a backward facing step. Particle image velocimetry technique was used to conducted refined velocity measurements over a reference smooth acrylic wall and rough walls produced from sandpaper 36 and 24 grits positioned downstream of a backward facing step, one after another. Each experiment was conducted at Reynolds number based on the step height and centerline mean velocity of 7050. The results showed that sandpaper 36 and 24 grits increased the reattachment length by 5% and 7%, respectively, compared with the value obtained over the smooth wall. The distributions of the mean velocities, Reynolds stresses, triple velocity correlations and turbulence production are used to examine roughness effects on the flow field downstream of the backward facing step. Two-point auto-correlation function and proper orthogonal decomposition (POD) are also used to investigate the impact of wall roughness on the large scale structures.

Identiferoai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:MWU.1993/23265
Date16 January 2014
CreatorsEssel, Ebenezer Ekow
ContributorsTachie, Mark (Mechanical and Manufacturing Engineering), Kuhn David (Mechanical and Manufacturing Engineering) Clark, Shawn (Civil Engineering)
Source SetsLibrary and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada
Detected LanguageEnglish

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